WASHINGTON — Republican Sen. Lamar Alexander said Tuesday he will step down from the ranks of Senate GOP leadership, leaving the No. 3 job in January. He also decided against seeking the No. 2 job of GOP whip.

In a speech to the Senate, the two-term Tennessee lawmaker said quitting the leadership will allow him to focus more on helping a deeply divided Senate — where 60 votes out of 100 are needed to advance virtually any major legislation — become a more effective institution. He said he will concentrate on reining in health care spending and job creation.

“Stepping down from the Republican leadership will liberate me to spend more time trying to work toward results on the issues I care the most about,” he said.

Alexander, 71, was elected to a second term in 2008. He insisted he will seek re-election in 2014.

In talking about consensus building, Alexander described himself as a “very Republican Republican,” but he said senators do their jobs with excessive civility. He rejected the notion that Congress is overly divisive and cited more egregious examples from U.S. history — Vice President Aaron Burr killing Treasury Secretary Alexander Hamilton in an 1804 duel, Rep. Sam Houston caning an Ohio lawmaker and venomous debates during the Civil War, the Army-McCarthy hearings, Watergate and Vietnam.

“To suggest that we should be more timid in debating the issues is to ignore American history and the purpose of the Senate,” Alexander said.

Alexander’s departure leaves an opening as head of the Senate Republican Conference. The retirement of Sen. Jon Kyl, R-Ariz., creates an opportunity for a Republican to fill the No. 2 job of Senate GOP whip.